U.S. patent number 10,692,641 [Application Number 15/952,364] was granted by the patent office on 2020-06-23 for method of additively manufacturing an impedance transformer.
This patent grant is currently assigned to Raytheon Company. The grantee listed for this patent is Raytheon Company. Invention is credited to Patrick J. Kocurek, Christopher A. Loehrlein, Brandon W. Pillans, Daniel B. Schlieter.
United States Patent |
10,692,641 |
Schlieter , et al. |
June 23, 2020 |
Method of additively manufacturing an impedance transformer
Abstract
A transmission line impedance transformer including at least two
different dielectric media having different dielectric properties,
each of the dielectric media being configured to taper in thickness
along the length of the impedance transformer in an inverse
relationship with respect to each other so as to form a combined
dielectric medium having an effective dielectric property that is
graded along the transmission path. The two or more dielectric
media may be disposed between two conductors to provide an
impedance transformer in which a characteristic impedance of the
transmission line varies along its length in response to the
gradation of the effective dielectric property of the combined
dielectric medium.
Inventors: |
Schlieter; Daniel B.
(Richardson, TX), Kocurek; Patrick J. (Allen, TX),
Loehrlein; Christopher A. (Murphy, TX), Pillans; Brandon
W. (Plano, TX) |
Applicant: |
Name |
City |
State |
Country |
Type |
Raytheon Company |
Waltham |
MA |
US |
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Assignee: |
Raytheon Company (Waltham,
MA)
|
Family
ID: |
57518007 |
Appl.
No.: |
15/952,364 |
Filed: |
April 13, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180233269 A1 |
Aug 16, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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15004534 |
Jan 22, 2016 |
9966180 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01P
3/082 (20130101); H01F 27/28 (20130101); H01F
41/04 (20130101) |
Current International
Class: |
H01F
7/06 (20060101); H01F 41/04 (20060101); H01P
3/08 (20060101); H01F 27/28 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1410461 |
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Aug 2011 |
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EP |
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767 067 |
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Jan 1957 |
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GB |
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02/101871 |
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Dec 2002 |
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WO |
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2012/128404 |
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Sep 2012 |
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WO |
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2015000057 |
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Jan 2015 |
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WO |
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Other References
International Search Report and Written Opinion of the
International Searching Authority dated Feb. 6, 2017, for
corresponding PCT Application No. PCT/US2016/063320. cited by
applicant .
Yamasaki: "Scattering of electromagnetic waves by inhomogeneous
dielectric gratings with parallel perfectly conducting
strips-Matrix formulation of point matching method",
Electromagnetic Theory (EMTS), Proceedings of 2013 URSI
International Symposium on IEEE, May 20, 2013, pp. 767-770. cited
by applicant .
Dreher et al.: "Analysis of Microstrip Lines in Multilayer
Structures of Arbitrarily Varying Thickness", IEEE Microwave and
Guided Wave Letters, IEEE Inc., New York, U.S., vol. 10, No. 2,
Feb. 1, 2000. cited by applicant.
|
Primary Examiner: Kim; Paul D
Attorney, Agent or Firm: Renner, Otto, Boisselle &
Sklar, LLP
Parent Case Text
RELATED APPLICATIONS
This application is a continuation of U.S. application Ser. No.
15/004,534 filed on Jan. 22, 2016, now U.S. Pat. No. 9,966,180
which is hereby incorporated herein by reference in its entirety.
Claims
What is claimed is:
1. A method of additively manufacturing an impedance transformer
comprising: providing at least one conductor; and forming at least
one dielectric medium at least partially overlying the at least one
conductor, the at least one dielectric medium being formed from a
dielectric material; wherein the forming the at least one
dielectric medium includes sequentially additively forming
individual layers of the dielectric material on top of each other
along predetermined layer paths; wherein during the forming of at
least some of the individual layers, a composition of the
dielectric material is varied along at least a portion of the
respective layer paths to provide a variable dielectric property
along at least a portion of the at least one dielectric medium; and
wherein the composition of the dielectric material is configured to
vary by changing an amount of one or more dielectric constituent
materials contained in the dielectric material.
2. The method according to claim 1, wherein the amount of the one
or more dielectric constituent materials contained in the
dielectric material is configured to continuously increase or
decrease along a propagation direction of the impedance transformer
to thereby provide a corresponding continuous increase or decrease
in the dielectric property, whereby a characteristic impedance of
the impedance transformer is configured to continuously increase or
decrease in response to the corresponding continuous increase or
decrease in the dielectric property caused by the change in the
composition of the dielectric material.
3. The method according to claim 1, wherein the dielectric material
includes a polymeric binder and the one or more dielectric
constituent materials are contained in the polymeric binder, and
the composition of the dielectric material is configured to vary by
changing a ratio of the amount of the one or more dielectric
constituent materials relative to an amount of the binder.
4. The method according to claim 1, wherein the one or more
dielectric constituent materials include one or more of: silica,
alumina, ferrite-doped calcium titanate, magnesium, strontium,
niobium, ferrite-doped calcium titanate zirconate, ferrite-doped
barium titanate zirconate, niobium-doped calcium titanate
zirconate, and niobium-doped barium titanate zirconate.
5. The method according to claim 1, further comprising a step of
solidifying the dielectric material following each sequential
forming of the individual layers along the predetermined layer
paths.
6. The method according to claim 5, wherein the solidifying
includes at least one of: air drying, temperature treatment, and UV
curing.
7. The method according to claim 1, wherein the sequentially
additively forming individual layers of the dielectric material
includes depositing of the individual layers from an extruder.
8. The method according to claim 1, wherein the impedance
transformer is additively manufactured in situ into a radio
frequency module.
9. The method according to claim 8, wherein during the additive
manufacturing of the impedance transformer in situ in the radio
frequency module, the impedance transformer is configured to extend
along circuitous paths or up a vertical surface of the radio
frequency module.
10. A method of additively manufacturing an impedance transformer
comprising: providing at least one conductor; and forming at least
one dielectric medium at least partially overlying the at least one
conductor, the at least one dielectric medium being formed from a
dielectric material; wherein the forming the at least one
dielectric medium includes sequentially additively forming
individual layers of the dielectric material on top of each other
along predetermined layer paths; wherein during the forming of at
least some of the individual layers, a composition of the
dielectric material is varied along at least a portion of the
respective layer paths to provide a variable dielectric property
along at least a portion of the at least one dielectric medium; and
wherein the composition of the dielectric material is continuously
varied to provide a continuously graded effective dielectric
property along the portion of the at least one dielectric
medium.
11. The method according to claim 10, wherein the composition of
the dielectric material is configured to vary by changing an amount
of one or more dielectric constituent materials contained in the
dielectric material.
12. A method of additively manufacturing an impedance transformer
comprising: providing at least one conductor; and forming at least
one dielectric medium at least partially overlying the at least one
conductor, the at least one dielectric medium being formed from a
dielectric material; wherein the forming the at least one
dielectric medium includes sequentially additively forming
individual layers of the dielectric material on top of each other
along predetermined layer paths; wherein during the forming of at
least some of the individual layers, a composition of the
dielectric material is varied along at least a portion of the
respective layer paths to provide a variable dielectric property
along at least a portion of the at least one dielectric medium; and
wherein the providing the at least one conductor includes forming
the at least one conductor by sequentially additively forming
individual layers of a conductor material along predetermined layer
paths via an additive manufacturing technique.
13. The method according to claim 12, wherein during the forming of
the at least one conductor, a composition of the conductor material
is varied along a length of the conductor to vary the electrical
property of the conductor along a propagation direction of the
impedance transformer.
14. The method according to claim 13, wherein the composition of
the conductor material is varied to vary the electrical resistivity
of the at least one conductor, which thereby varies a
characteristic impedance of the impedance transformer in the
propagation direction.
15. A method of additively manufacturing an impedance transformer
comprising: providing at least one conductor; and forming at least
one dielectric medium at least partially overlying the at least one
conductor, the at least one dielectric medium being formed from a
dielectric material; wherein the forming the at least one
dielectric medium includes sequentially additively forming
individual layers of the dielectric material on top of each other
along predetermined layer paths; wherein during the forming of at
least some of the individual layers, a composition of the
dielectric material is varied along at least a portion of the
respective layer paths to provide a variable dielectric property
along at least a portion of the at least one dielectric medium;
wherein the at least one conductor is a first conductor, the method
further comprising a step of providing a second conductor opposite
the first conductor, in which the at least one dielectric medium is
interposed between the first conductor and the second conductor;
wherein the first conductor and the second conductor are each
configured to extend between opposite ends of the impedance
transformer to establish a propagation direction for propagating an
electromagnetic wave between opposite ends of the impedance
transformer when in use; wherein the at least one dielectric medium
is formed to extend from one end of the impedance transformer to
the opposite end of the impedance transformer in the propagation
direction; and wherein the composition of the dielectric material
of the at least one dielectric medium is continuously varied from
one end of the impedance transformer to an opposite end of the
impedance transformer to provide a continuously graded effective
dielectric property along the impedance transformer.
16. A method of additively manufacturing an impedance transformer
comprising: providing at least one conductor; and forming at least
one dielectric medium at least partially overlying the at least one
conductor, the at least one dielectric medium being formed from a
dielectric material; wherein the forming the at least one
dielectric medium includes sequentially additively forming
individual layers of the dielectric material on top of each other
along predetermined layer paths; wherein during the forming of at
least some of the individual layers, a composition of the
dielectric material is varied along at least a portion of the
respective layer paths to provide a variable dielectric property
along at least a portion of the at least one dielectric medium;
wherein the sequentially additively forming individual layers of
the dielectric material includes depositing of the individual
layers from an extruder; and wherein the depositing of the
individual layers includes a micro-dispense technique or a fused
deposition modeling technique.
17. A method of additively manufacturing an impedance transformer
comprising: providing at least one conductor; and forming at least
one dielectric medium at least partially overlying the at least one
conductor, the at least one dielectric medium being formed from a
dielectric material; wherein the forming the at least one
dielectric medium includes sequentially additively forming
individual layers of the dielectric material on top of each other
along predetermined layer paths; wherein during the forming of at
least some of the individual layers, a composition of the
dielectric material is varied along at least a portion of the
respective layer paths to provide a variable dielectric property
along at least a portion of the at least one dielectric medium;
wherein the sequentially additively forming individual layers of
the dielectric material includes depositing of the individual
layers from an extruder; and wherein the dielectric material is a
dielectric paste having a polymeric binder and one or more
dielectric constituent materials contained in the polymeric binder,
and wherein during the depositing of the individual layers of the
dielectric paste from the extruder, the extruder moves across a
build area in a direction of the predetermined layer path.
18. A method of additively manufacturing an impedance transformer
comprising: providing at least one conductor; and forming at least
one dielectric medium at least partially overlying the at least one
conductor, the at least one dielectric medium being formed from a
dielectric material; wherein the forming the at least one
dielectric medium includes sequentially additively forming
individual layers of the dielectric material on top of each other
along predetermined layer paths; wherein during the forming of at
least some of the individual layers, a composition of the
dielectric material is varied along at least a portion of the
respective layer paths to provide a variable dielectric property
along at least a portion of the at least one dielectric medium;
wherein the impedance transformer is additively manufactured in
situ into an impedance matching system, the impedance matching
system having a first circuit with a first impedance characteristic
and a second circuit with a second impedance characteristic
different from the first impedance characteristic, and wherein the
impedance transformer is additively manufactured in situ to include
an input configured to connect to the first circuit, and to include
an output configured to connect to the second circuit.
Description
FIELD OF INVENTION
The present invention relates generally to impedance transformers,
and more particularly to additively manufactured impedance
transformers having a graded dielectric property.
BACKGROUND
Electronic modules, such as radio frequency (RF) modules, typically
contain RF circuits, transmission lines, high power amplifiers, and
antenna elements that are commonly manufactured on specially
designed substrate boards. For the purposes of such circuits, it is
important to maintain control over impedance characteristics. If
the impedance of different parts of the circuit do not match, this
may result in inefficient power transfer, unnecessary heating of
components, or various other problems. To minimize these problems,
a transmission line impedance transformer matching network is
commonly utilized in such circuits, for example, to match
relatively low impedances at the gate and drain of field effect
transistors (FETs) in the circuit with relatively high impedances
needed in other parts of the circuit.
One factor affecting the performance of such transmission line
impedance transformer matching networks is the dielectric property
of the impedance transformer substrate medium, such as the
dielectric constant of the medium. For example, the dielectric
constant of the substrate medium affects the velocity of the signal
propagating through the medium, and therefore the electrical length
of the transmission line. In conventional RF design, an impedance
transformer substrate medium is typically selected with a
dielectric property value suitable for the design. Once the
substrate material is selected, the transmission line
characteristic impedance value may be exclusively adjusted by
controlling the impedance transformer geometry and physical
structure.
As the trend toward miniaturizing such RF modules and circuits
continues, the ability to maintain the performance attributes of
such circuits becomes increasingly difficult. For example,
increasing the power and bandwidth of a high-power amplifier used
in an RF circuit may be a common design criteria, but enhancing
these attributes while maintaining a compact size of the circuit is
difficult, if not often impractical. For example, while a
transmission line transformer output matching network may be
utilized to provide good bandwidth and excellent power output for
the amplifier, such utilization is often at the expense of
increased size and fabrication difficulty of the impedance
transformer and circuit. As such, designers will typically be
forced to trade one desired specification (e.g., power, bandwidth,
size, or fabrication difficulty) so as to satisfy another one of
these desired specifications.
SUMMARY OF INVENTION
The present invention provides an impedance transformer for a
transmission line that has at least one gradually varied effective
dielectric property along its length, which improves the overall
performance of the transmission line, while also enhancing design
flexibility and improving integration of such devices.
The exemplary impedance transformer may include a substrate having
at least two different dielectric materials with different
dielectric properties. Each of the dielectric materials may be
configured to taper in thickness along the length of the impedance
transformer in an inverse relationship to each other so as to
provide an effective dielectric property that is graded along the
length of the impedance transformer.
For example, a first dielectric medium and a second dielectric
medium having different dielectric properties may each be
configured as wedge-shaped members such that each medium has an
inclined area and a tapered thickness. The wedge-shaped media may
be disposed in an inverse relationship with respect to each other
such that respective inclined areas interface with each other and
the respective tapered thicknesses reduce in opposite directions.
In this manner, the effective dielectric property of the combined
dielectric medium may progressively increase or decrease
corresponding with the relative change in thicknesses of the first
dielectric medium (having a first dielectric property) and the
second dielectric medium (having a second different dielectric
property) along the length of the impedance transformer.
The dielectric property of each dielectric medium, or the effective
dielectric property of the combined dielectric medium, may include
one or more dielectric properties, such as permittivity (also
referred to as relative permittivity, .sub.r, or dielectric
constant), permeability (also referred to as relative permeability
or .mu..sub.r), and conductivity (or its inverse, resistivity).
The two or more dielectric media may be disposed between two
conductors to provide an impedance transformer in which a
characteristic impedance of the transmission line varies along its
length corresponding with the gradation of the effective dielectric
property of the combined dielectric medium. In this manner, the
exemplary impedance transformer may be used in a transmission line
impedance transformer matching network to match the impedance
characteristics from one circuit to another circuit.
Such an impedance transformer having a graded effective dielectric
property or properties along its length enables a reduction in the
number of discontinuities and abrupt changes in the transmission
path between dielectric media, which may improve performance of the
transmission line, and may also improve ease of manufacturing and
associated costs. In addition, by reducing the number of interfaces
or discontinuities along the transmission path, the reliability of
the device may also improve since each interface is also a
potential stress concentration during operation, which can lead to
premature failure of the device during temperature cycling.
Such an impedance transformer used in a transmission line impedance
matching network may also enable more efficient matching of the
impedance characteristics of one circuit with another, while
enabling higher power capabilities and increased bandwidth, and
while also minimizing the size of such matching networks and signal
loss.
To facilitate the manufacturing of such an impedance transformer,
the two or more dielectric media may be formed by an additive
manufacturing process, for example, layerwise deposition or 3D
printing. By additive manufacturing such impedance transformers,
the fabrication of such media structures may be simplified with
fewer steps. In addition, the tailorability and flexibility of the
impedance transformer and corresponding circuit design may be
improved. For example, such impedance transformers may be
additively formed in situ within an RF module or directly
integrated into circuits, and may be free-formed with circuitous
paths around other circuit components, or may even be formed to
extend vertically up RF module walls.
According to an aspect of the invention, an impedance transformer
includes at least one dielectric medium configured such that the
impedance transformer has at least one gradually varied effective
dielectric property along its length.
According to another aspect of the invention, an impedance
transformer includes a first dielectric medium having a first
dielectric property, the first dielectric medium having a first
inclined area to define a tapered thickness of the first dielectric
medium that reduces in a first direction along a length of the
impedance transformer; and a second dielectric medium having a
second dielectric property different from the first dielectric
property, the second dielectric medium having a second inclined
area to define a tapered thickness of the second dielectric medium
that reduces in a direction opposite the first direction along the
length of the impedance transformer; where the second dielectric
medium is disposed in an inverse relationship to the first
dielectric medium such that the first inclined area interfaces with
the second inclined area.
The impedance transformer may further include a first conductor and
a second conductor, where the first dielectric medium and the
second dielectric medium are disposed between the first conductor
and the second conductor.
Embodiments of the invention may include one or more of the
following additional features separately or in combination.
For example, the first dielectric medium may have a lower substrate
surface extending along the length of the impedance transformer,
the lower substrate surface being opposite the first inclined area
and defining the tapered thickness of the first dielectric medium
therebetween.
The second dielectric medium may have an upper substrate surface
extending along the length of the impedance transformer, the upper
substrate surface being opposite the second inclined area and
defining the tapered thickness of the second dielectric medium
therebetween.
The lower substrate surface and the upper substrate surface may be
substantially planar surfaces.
The first conductor may be disposed on the lower substrate surface
and the second conductor may be disposed on the upper substrate
surface.
The lower substrate surface may be substantially parallel to the
upper substrate surface.
The interface between the first dielectric medium and the second
dielectric medium may be inclined with respect to a plane
perpendicular to the lower and/or upper substrate surfaces.
The first dielectric medium and the second dielectric medium may
have substantially the same width in a direction transverse to the
first direction.
The respective widths of the first dielectric medium and the second
dielectric medium may be substantially constant along the length of
the impedance transformer.
The first dielectric medium and the second dielectric medium may be
substantially wedge shaped.
The first dielectric medium and/or the second dielectric medium may
have a maximum thickness at one end that is at least twice the
minimum thickness at an opposite end.
The first dielectric property of the first dielectric medium may
include a first dielectric constant, and the second dielectric
property of the second dielectric medium may include a second
dielectric constant.
The first dielectric constant may be at least five times greater
than the second dielectric constant, or the second dielectric
constant may be at least five times greater than the first
dielectric constant.
At least one of the first dielectric medium and the second
dielectric medium may have a graded effective dielectric property
along its length.
The first dielectric medium and the second dielectric medium may
define a combined dielectric medium, and the effective dielectric
property of the combined dielectric medium may progressively
increase or decrease along the length of the impedance
transformer.
For example, the effective dielectric property of the combined
dielectric medium may progressively increase or decrease in the
first direction corresponding with the relative change in
thicknesses of the first dielectric medium and the second
dielectric medium along the length of the impedance
transformer.
The impedance transformer may further comprises an input port for
communicating with an input circuit having a first impedance
characteristic, and an output port for communicating with an output
circuit having a second different impedance characteristic.
The impedance transformer may have a characteristic impedance that
is variable along its length so as to match the first impedance
characteristic of the first circuit with the second impedance
characteristic of the second circuit.
The variation in the characteristic impedance of the impedance
transformer may at least partially correspond with the change in
effective dielectric property of the combined dielectric medium
along the length of the impedance transformer.
The impedance transformer may extend in a serpentine path.
The first dielectric medium and/or the second dielectric medium may
be formed by an additive manufacturing process.
The first conductor and/or the second conductor may be formed by an
additive manufacturing process.
The first dielectric medium and the second dielectric medium may be
formed from a paste that is deposited by a layerwise additive
manufacturing process.
According to another aspect of the invention, a method of
manufacturing an impedance transformer includes: (i) forming a
first dielectric medium from a first dielectric material having a
first dielectric property, the first dielectric medium being formed
to have a first inclined area and a tapered thickness that reduces
in a first direction along a length of the impedance transformer;
and (ii) forming a second dielectric medium from a second
dielectric material having a second dielectric property different
from the first dielectric property, the second dielectric medium
being formed to have a second inclined area and a tapered thickness
that reduces in a direction opposite the first direction along the
length of the impedance transformer; where the second dielectric
material is formed on the first dielectric medium in an inverse
relationship to the first dielectric medium such that the first
inclined area of the first dielectric medium interfaces with the
second inclined area of the second dielectric medium.
The method of manufacturing an impedance transformer may include
one or more of the following additional features separately or in
combination.
For example, the method may further include: (i) forming a first
conductor from a conductive material; and (ii) forming a second
conductor from a conductive material; where the first dielectric
medium and the second dielectric medium may be disposed between the
first conductor and the second conductor.
Optionally, during the forming of the first dielectric medium
and/or the second dielectric medium, the effective dielectric
property of the first dielectric medium and/or the second
dielectric medium may be graded along the length of the impedance
transformer.
Alternatively or additionally, during the forming of the first
conductor and/or the second conductor, the electrical conductivity
of the first conductor and/or the second conductor may be graded
along the length of the impedance transformer.
The method may further include solidifying at least one of the
first conductor, the second conductor, the first dielectric medium,
and the second dielectric medium after the respective forming
steps.
The first conductor, the second conductor, the first dielectric
medium, and the second dielectric medium may each be formed by
deposition in a layerwise additive manufacturing process.
The first dielectric medium and the second dielectric medium may
define a combined dielectric medium that is formed by depositing
individual layers of dielectric material in a layerwise additive
manufacturing process.
The first dielectric medium and the second dielectric medium may be
deposited in a single extrusion step to define each individual
layer.
The first dielectric medium and the second dielectric medium may
each have an effective dielectric property that is graded along the
length of the impedance transformer.
The following description and the annexed drawings set forth
certain illustrative embodiments of the invention. These
embodiments are indicative, however, of but a few of the various
ways in which the principles of the invention may be employed.
Other objects, advantages and novel features according to aspects
of the invention will become apparent from the following detailed
description when considered in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The annexed drawings, which are not necessarily to scale, show
various aspects of the invention.
FIG. 1 is a perspective view of an exemplary impedance transformer
according to the invention.
FIGS. 2A-2E are cross-sectional views of alternative embodiments of
the exemplary impedance transformer.
FIG. 3 is a cross-sectional view of another exemplary impedance
transformer formed by a layerwise additive manufacturing press.
DETAILED DESCRIPTION
A transmission line impedance transformer, such as for a
transmission line impedance matching network, may include at least
two different dielectric media having different dielectric
properties, each of the dielectric media being configured to taper
in thickness along the length of the impedance transformer in an
inverse relationship with respect to each other so as to form a
combined dielectric medium having an effective dielectric property
that is graded along the transmission path. The two or more
dielectric media may be disposed between two conductors to provide
an impedance transformer in which a characteristic impedance of the
transmission line varies along its length in response to the
gradation of the effective dielectric property of the combined
dielectric medium.
The principles of the present invention have particular application
to RF circuits having microwave circuit impedance transformers or
transmission lines, amplifiers and module
interconnects/transistors, filters, power dividers and couplers,
MMIC or ASIC circuits, etc., and thus will be described below
chiefly in this context. It is understood that the impedance
matching networks and techniques described herein are not limited
to any particular type of RF circuit, or RF application. Rather, it
is understood that principles of this invention may be applicable
in a wide variety of radio frequency (RF) systems, circuits, and
other devices where it is desirable to provide impedance matching
between different parts of a circuit by using an impedance
transformer that gradually varies a dielectric property so as to
reduce abrupt discontinuities between the dielectric media, which
may improve overall performance, design flexibility, and
manufacturing costs, among other considerations. It should also be
understood that the impedance transformer and related line matching
techniques described herein are not limited to implementation on or
with any particular type of RF transmission media and that the
impedance transformer with a graded dielectric property or
properties may be implemented in a variety of different RF
transmission media including, but not limited to: microstrip,
buried microstrip, stripline, twinline, slotline, co-planar
waveguide, and suspended air stripline.
The term "dielectric property" as used herein refers to one or more
of permittivity (also referred to as relative permittivity, .sub.r,
or dielectric constant), permeability (also referred to as relative
permeability or .mu..sub.r), and electrical conductivity (or
electrical resistivity).
In the discussion above and to follow, the terms "upper", "lower",
"top", "bottom," "end," "inner," "outer," "above," "below," etc.
refer to the impedance transformer as viewed in a horizontal
position, as shown in FIG. 1. This is done realizing that these
devices, such as when used in electronic modules mounted to
vehicles, can be mounted on the top, bottom, or sides of other
components, or can be inclined with respect to the vehicle chassis,
or can be provided in various other positions.
Turning now to FIG. 1, an exemplary impedance transformer 10 is
shown. In the illustrated embodiment, the impedance transformer 10
is configured as a microstrip transmission line having a dielectric
medium, or substrate, 12 disposed between two conductors 14, 16 on
opposite sides. The first conductor 14 may be configured as a
ground plane conductor and the second conductor 16 may be
configured as a transmission line for propagating an electrical
signal along the length (L) of the impedance transformer 10. The
dielectric medium 12 may be configured as a combined dielectric
medium having a first dielectric medium 18 and a second dielectric
medium 20. The first dielectric medium 18 may have a first
dielectric property (for example, a first dielectric constant), and
the second dielectric medium 20 may have a second dielectric
property (for example, a second dielectric constant) that is
different from the first dielectric property.
As shown in the illustrated embodiment, the first dielectric medium
18 may have a lower (first) substrate surface 22 extending along
the length (L) of the impedance transformer and an inclined area 24
that is opposite the lower substrate surface 22, which defines a
tapered thickness (T1) of the first dielectric medium 18
therebetween. The second dielectric medium 20 may have an upper
(second) substrate surface 26 extending along the length of the
impedance transformer and an inclined area 28 that is opposite the
upper substrate surface 26, which defines a tapered thickness (T2)
of the second dielectric medium 20 therebetween. The second
dielectric medium 20 may be disposed in an inverse relationship
with respect to the first dielectric medium 18 such that the first
inclined area 24 is adjacent to and interfaces with the second
inclined area 28 and the respective tapered thicknesses T1, T2
progressively reduce in opposite directions.
By providing the at least two different dielectric media 18, 20
having different dielectric properties, a variable "effective"
dielectric property of the combined medium 12 may be obtained. The
effective dielectric property (for example, the effective
dielectric constant, .sub.eff) may be defined as the dielectric
property that an electrical signal experiences when propagating
along the transmission line 16 in the vicinity of the dielectric
media 18, 20, which is at least partially dependent on the
electromagnetic (EM) wave that exists in the respective dielectric
media 18, 20. The effective dielectric property may be determined
by the local overall thickness of the combined dielectric medium 12
and the local relative thickness of each medium 18, 20 along the
transmission path, such that the resulting effective dielectric
property obtains a value between the dielectric property value of
each medium 18, 20.
So as to establish a communicating relationship of EM wave
propagation between the two different dielectric media 18, 20, the
first inclined area 24 may cooperate or couple in a complementary
manner with the second inclined area 28 at the interface between
media 18, 20. Generally, the interfacial area between the first
dielectric medium 18 and the second dielectric medium 20 may be
inclined with respect to a plane perpendicular to a longitudinal
axis extending along the length of the impedance transformer. In
this manner, the effective dielectric property of the combined
dielectric medium 12 may gradually and uniformly increase (or
decrease) corresponding with the relative change in thicknesses of
the first dielectric medium 18 and the second different dielectric
medium 20 along the length of the impedance transformer 10. For
example, as the first dielectric medium 18 (having a first
dielectric property, such as a first dielectric constant)
progressively decreases in thickness along the length of the
impedance transformer, and as the second dielectric medium (having
a second different dielectric property, such as a second dielectric
constant) progressively increases in thickness along the length of
the impedance transformer 10, the effective dielectric property
(for example, the effective dielectric constant) of the combined
medium 12 may increase (or decrease) along the length of the
impedance transformer 10, depending on the relative thicknesses of
the dielectric media 18, 20, and whether the second dielectric
property is greater (or less) than the first dielectric
property.
For example, the effective dielectric property of the combined
dielectric medium 12 may be graded by gradually increasing the
effective dielectric constant of the combined dielectric medium 12
along the transmission path. For example, this may be achieved by
providing the second dielectric medium 20 with a higher dielectric
constant than the first dielectric medium 18. By gradually
increasing the effective dielectric constant along the transmission
path, the characteristic impedance of the transmission line may be
gradually increased and the propagation velocity of the EM signal
in the transmission line may be deliberately slowed, known as a
slow-wave effect, which increases the electrical length per unit
physical length and which may allow for circuit compaction.
In this manner, the variation in the characteristic impedance of
the transmission line 16 may be at least partially determined by
the gradation in the effective dielectric property (e.g., the
effective dielectric constant) of the combined dielectric medium 12
along the length of the impedance transformer 10. This may enable
the impedance transformer 10 to be usefully employed in a
transmission line impedance matching system or network that is
configured to match the impedance characteristic from one circuit
to another circuit having a different impedance characteristics. As
such, the impedance transformer 10 may include an input port (e.g.,
one end of the transmission line 16) for communicating with an
input circuit having a first impedance characteristic, and an
output port (e.g., an opposite end of the transmission line 16) for
communicating with an output circuit having a second different
impedance characteristic. The characteristic impedance of the
transmission line 16 may be determined by a number of factors other
than the effective dielectric property of the combined medium 12,
including the width and thickness of the top conductor 16, and the
spacing between the elongated conductors 14, 16, as well as other
characteristics of the respective media 18, 20.
Generally, if a circuit has an exceptionally high or low impedance,
it is usually difficult to create an impedance transformer that has
the desired characteristic impedance for matching into the circuit,
and that fits within the size limitations of the circuit. One known
technique for impedance matching is to provide a single dielectric
substrate (e.g., having a single dielectric constant) with a
relatively long taper (i.e., Klopfenstein taper or
stepped-impedance taper). However, such single-dielectric tapered
impedance transformers are often impractically too narrow to
achieve high impedance values, or are impractically too wide to
achieve low impedance values. In addition, such single-dielectric
tapered impedance transformers do not usually fit well onto a
circuit, substrate, or MMIC having a limited aspect ratio
(length-to-width ratio) or otherwise constrained real estate
limitations.
Another known technique for impedance matching is to provide
discrete cuboid segments of different dielectric media (having
different dielectric constants) along the length of the
transmission line, which connect at vertical interfaces
perpendicular to the transmission path. However, such discrete
cuboid segments do not gradually increase or decrease the effective
dielectric property of the medium over the length of the
transformer, and instead results in abrupt step-wise changes in the
dielectric property from one material to another. These abrupt
step-wise changes in the dielectric property (e.g., at the vertical
interfaces) may adversely affect the performance characteristics of
the device by causing undesirable scattering and reflections of the
signal, which results in a net increase in transmission loss.
The exemplary impedance transformer described herein enables a
wider range of impedance transformation that can be practically
achieved (e.g., with practical widths) over a broader bandwidth and
with higher power capabilities than would otherwise be possible
with only a single tapered transformer section. More particularly,
by providing the second dielectric medium 20 with a higher or lower
dielectric property than the first dielectric medium 18, the
effective dielectric property of the combined medium 12 may be
increased or decreased over shorter distances than would otherwise
be possible with a single dielectric material. For example, the
exemplary impedance transformer may be capable of leveraging a
relatively high dielectric constant of one of the dielectric media
(e.g., the first dielectric medium) to achieve low impedances, and
may be capable of leveraging a relatively low dielectric constant
of another dielectric medium (e.g., the second dielectric medium)
to achieve high impedances, while still providing a practical
(e.g., manufacturable) size of the device. In addition, by
interfacing the respective dielectric media 18, 20 in an inverse
relationship with respect to each other such that the effective
dielectric property is gradually changed over the length of the
impedance transformer 10 allows for fewer and less abrupt
discontinuities in the EM transmission path, which improves overall
performance of the impedance matching network. Accordingly, a
designer is provided with substantially greater flexibility with
regard to the range of characteristic impedances that can be
produced with the exemplary impedance transformer 10.
The exemplary impedance transformer 10 may also enable a wide range
of characteristic impedances by controlling the dielectric
properties of the respective dielectric media 18, 20 without the
need for altering the overall thickness of the combined medium 12
along the transmission path, or without the need for changing the
spacing between conductors 14, 16. For example, providing the first
dielectric medium 18 with a lower dielectric constant compared to
the second dielectric medium 20 can permit input of lines with
lower impedance as compared to what could otherwise be achieved
using a single conventional low dielectric substrate. In addition,
by maintaining such planarity of the impedance transformer 10, the
connections between circuits or other components may be improved
without the need for specially designed interconnections.
The exemplary impedance transformer 10 may also enable transmission
lines that are conventionally very wide to be reduced to a more
manageable width for reducing the overall size of the impedance
transformer and corresponding matching network. In other words,
unlike conventional single substrate tapered line transformers, the
exemplary impedance transformer 10 does not necessarily vary the
line impedance by continuously increasing the transmission line
width over the length of the transformer. Instead, the effective
dielectric property of the combined medium 12 may be gradually
varied over the length of the impedance transformer 10 so as to
progressively change the characteristic impedance over the length
of the transmission line 16. For example, selectively increasing
the dielectric constant of the second dielectric medium 20 may
permit higher impedance lines of practical width to be formed on
the substrate when such high impedance values would otherwise be
too narrow for practical implementation on a substrate.
So as to maintain planarity of the impedance transformer 10, the
first dielectric medium 18 and the second dielectric medium 20 may
each be configured as wedge-shaped members that are respectively
configured to define a combined dielectric medium 12 having a
rectangular parallepiped structure. The lower substrate surface 22
of the first dielectric medium 18 and the upper substrate surface
26 of the second dielectric medium 20 may be substantially planar
surfaces, which may be substantially parallel to each other on
opposite sides of the combined dielectric medium 12. In the
exemplary microstrip configuration, the first conductor 16 may be
disposed on the lower substrate surface 22 and the second conductor
14 may be disposed on the upper substrate surface 26, each of which
extend along the length (L) of the impedance transformer in the
direction of the signal transmission path. In addition, the first
dielectric medium 18 and the second dielectric medium 20 may have
the same width (W), which may be substantially constant along the
length of the impedance transformer 10.
In some non-limiting embodiments, the first dielectric medium 18
and the second dielectric medium 20 may each have a maximum
thickness at one end in a range between 0.13 mm to 0.4 mm, and a
minimum thickness at an opposite end in a range between 0.02 mm to
0.13 mm. In addition, the first dielectric medium 18 and the second
dielectric medium 20 may each have a maximum width (W) in a range
between 0.02 mm to 5 mm. The overall length (L) of the impedance
transformer may be about 5 mm to 10 mm, or greater. The dielectric
constant of the first dielectric medium may be in the range between
about 1 to 10, and the dielectric constant of the second dielectric
medium may be in the range between about 20 to 50. The exemplary
impedance transformer may match an input impedance of about 5 ohm
to an output impedance of about 50 ohm with 10:1 or greater
bandwidth and having a signal loss of less than 1 dB at 200W power
output. The exemplary impedance transformer may have a minimal
footprint, and may fit within an area of less than about 65
cm.sup.2, preferably fitting within an area of only about 5
cm.times.5 cm.
It is understood that other configurations of the exemplary
impedance transformer 10 are possible. For example, although the
inclined interfacial area between the first medium 18 and the
second medium 20 may bisect the rectangular parallelepiped
structure of the combined dielectric medium 12 (as shown in FIG.
1), it is also possible that the first dielectric medium 18 may
constitute a larger or smaller segment of the combined dielectric
medium 12 compared to that of the second dielectric medium 20 (as
shown in FIGS. 2A and 2B, for example). It is also possible that
the interfacial area between media 18, 20 may be curved, for
example, the respective inclined areas 24, 28 may be configured as
concave or convex areas (as shown in FIG. 2C, for example). In
addition, it is understood that the first dielectric medium may
instead increase in thickness along the transmission direction as
the second dielectric medium inversely reduces in thickness. Also,
the widths of the respective media 18, 20 and the overall thickness
of the combined medium 12 may be held constant along the length of
the impedance transformer 10, or the respective widths or overall
thickness may be different or may vary along the length of the
impedance transformer 10.
It is further understood that although the impedance transformer 10
may have only a single first dielectric medium 18 and a single
second dielectric medium 20 that define the combined dielectric
medium 12 and which constitute the entire length of the impedance
transformer 10, it is also possible that more than two different
dielectric media may be provided in the impedance transformer 10.
For example, the first dielectric medium 18 and the second
dielectric medium 20 may be provided as only one combined media
section of a plurality of combined media sections along the length
of the impedance transformer 10. The remaining plurality of media
sections may repeat the pattern of the first medium 18 and second
medium 20 along the remainder of the impedance transformer length,
or the remaining sections may further vary the dielectric property
(e.g., dielectric constant). Alternatively or additionally, the
other media may have different dielectric properties from both the
first medium 18 and second medium 20, for example, subsequent media
may be disposed having progressively increasing dielectric
constants along the impedance transformer length. The subsequent
media may be interfaced and configured in a similar manner as the
first medium 18 and second medium 20 to create a multiple-section,
progressively increasing graded dielectric media along the length
of the impedance transformer 10 (as shown in FIG. 2D, for
example).
The foregoing approach of varying the effective dielectric property
is not limited to use with microstrip constructions as shown in
FIG. 1. Rather, these techniques may be used with any other line
structure that is formed on a dielectric substrate, for example,
buried microstrip, stripline, slotline and co-planar waveguide
circuits where selected regions of the dielectric media above or
below the transmission line have modified dielectric properties, as
discussed above.
The dielectric materials for the media 18, 20 may be selected in a
suitable manner depending on the effective dielectric property and
impedance matching characteristics sought to be obtained. For
example, through selection of suitable materials, the first
dielectric medium may have a dielectric constant of about 1, and
the second dielectric medium may have a dielectric constant of
about 100, such that the effective dielectric constant of the
combined medium 12 is about 1 at the first end, about 50 in the
middle, and about 100 at the opposite end. Alternatively, the first
dielectric medium may have a dielectric constant of about 100, and
the second dielectric medium may have a dielectric constant of
about 1, such that the effective dielectric constant of the
combined medium 12 is about 100 at the first end, about 50 in the
middle, and about 1 at the opposite end. Other combinations are
possible, and the actual values and precise rate at which each of
these dielectric characteristics can be varied over the length of
the impedance transformer 10 will depend upon the particular design
characteristics of the transformer and the range of impedance
characteristics sought to be obtained.
In the illustrated embodiment of FIG. 1, the dielectric property of
each dielectric medium 18, 20 may be substantially uniform
throughout each medium segment.
However, as shown in illustrated embodiment of FIG. 2E, it is also
possible that the effective dielectric property of each individual
medium 18, 20 may be continuously varied or graded (increasing or
decreasing) across the medium, for example, along the length of the
impedance transformer in the direction of the transmission path.
For example, the effective dielectric constant of the first medium
18 may be continuously graded such that the dielectric constant
value is about 1 toward the thicker end, about 25 toward the
middle, and about 50 toward the tapered end. The effective
dielectric constant of the second medium 20 may also be
continuously graded such that the dielectric constant value is
about 10 toward the tapered end, about 50 toward the middle, and
about 100 toward the thicker end. Other combinations are possible,
and the actual values and precise rate at which each of these
effective dielectric properties for each individual medium may be
varied will depend upon the desired design characteristics of the
impedance transformer.
The choice of a dielectric composition can provide effective
dielectric constants that gradually increase or decrease over a
range from less than 2 to about 2500. The dielectric materials can
be prepared by mixing with other materials, such as thermosets,
thermoplastic, or other binding media; or by including varying
densities of voided regions (which generally introduce air), all of
which may produce the desired dielectric constants, as well as
other potentially desired media properties.
For example, materials exhibiting a low dielectric constant (<2
to about 9) may include silica and/or alumina with varying
densities of voided regions. While neither silica nor alumina have
any significant magnetic permeability, magnetic particles may be
added to render these or any other material significantly magnetic,
which may generally increase the permittivity of the media
layer.
Materials exhibiting a medium dielectric constant are generally in
the range of about 70 to 500. As noted above, these materials may
be mixed with other materials or voids to provide a desired
dielectric constant. These materials can include ferrite doped
calcium titanate. Doping metals can include magnesium, strontium
and niobium. These materials have a range of 45 to 600 in relative
magnetic permeability.
For high value dielectric constants, ferrite or niobium doped
calcium or barium titanate zirconates may be used. These materials
have a dielectric constant of about 2200 to 2650. Doping
percentages for these materials are generally from about 1 to 10
volume percent. As noted above with respect to other materials,
these materials may be mixed with other materials or voids to
provide the desired effective dielectric constant.
To facilitate the fabrication of the exemplary impedance
transformer, the dielectric media and/or the conductors may be
formed by an additive manufacturing process. Referring to FIG. 3,
an exemplary embodiment of an impedance transformer 110 that is
formed by an additive manufacturing process is shown. The impedance
transformer 110 is substantially the same as the above-referenced
impedance transformer 10, and consequently the same reference
numerals but indexed by 100 are used to denote structures
corresponding to the same or similar structures in the impedance
transformer. In addition, the foregoing description of the
impedance transformer 10 is equally applicable to the impedance
transformer 110, except as noted below.
In the illustrated embodiment, the impedance transformer 110
includes a combined dielectric medium layer 112 disposed between
two conductors 114, 116 on opposite sides. The dielectric medium
112 includes a first dielectric medium 118 having a first
dielectric property (e.g., a first dielectric constant), and a
second dielectric medium 120 having a second different dielectric
property (e.g., a second dielectric constant). The first dielectric
medium 118 has an inclined area 124 and a tapered thickness, and
the second dielectric medium 120 has an inclined area 128 and a
tapered thickness. The second dielectric medium 120 is disposed in
an inverse relationship with respect to the first dielectric medium
118, such that the first inclined area 124 interfaces in a
communicating relationship with the second inclined area 128 and
the respective tapered thicknesses of the media 118, 120
progressively reduce in opposite directions.
In some embodiments, the combined dielectric medium 112, or the
individual dielectric media 118, 120, may be formed with a
dielectric material that may be deposited through a nozzle by way
of a layerwise additive manufacturing process, such as
micro-dispense. For example, the dielectric material may be a
dielectric paste that may be deposited as a series of single layers
142, or traces, as the nozzle moves across the build area. In this
manner, the individual media 118, 120, may be formed layer by layer
until reaching a desired shape or configuration. The term "layer"
as used herein means one or more levels, or of potentially
patterned strata, and not necessarily a continuous phase.
In some embodiments, each of the respective layers 142 of the first
dielectric medium 118 may be deposited to fully form the first
dielectric medium 118 before the layers of the second dielectric
medium 120 are deposited and formed. Optionally, the dielectric
paste may be solidified before subsequent layers 142 are deposited,
or after the entire first dielectric medium 118 structure is
formed. The dielectric paste may be solidified by such methods
including temperature treatment, air drying, UV curing, or other
suitable methods of solidification well-known in the art. In other
embodiments, a layer 142 of the first dielectric medium material
may be deposited, followed by an adjacent layer 142 of second
dielectric medium material. As each subsequent layer of the first
material is deposited on top of the lower layer, the length of the
first dielectric material layer may decrease; and as each
subsequent layer of the second material is deposited on top of the
lower layer and adjacent to the first dielectric material, the
length of second dielectric material layer may increase in such a
way as to provide an inverse relationship between the respective
media 118, 120, (as shown in FIG. 2, for example). Optionally, the
dielectric paste may be solidified (such as through temperature
treatment, air drying, UV curing, or other suitable methods) before
subsequent layers 142 are deposited on top of each other, or after
the entire combined media 112 structure is formed.
The conductors 114, 116 may likewise be additively manufactured in
a similar manner. For example, the first conductor 114 may be
deposited with an electrically conductive paste, and the dielectric
layers 142 of the first medium 118 and the second medium 120 may be
subsequently deposited on top of the first conductor 114. The
second conductor 116 may be deposited with an electrically
conductive paste on top of the dielectric media layers 142.
Optionally, the electrically conductive paste may be solidified,
such as through temperature treatment or air drying, before
subsequent layers 142 are deposited. The foregoing approach of
additive manufacturing is not limited to microstrip constructions,
and may be used with other line structures, such as buried
microstrip, stripline, coplanar waveguide, slotline, etc.
Depending at least in part on the shape of the orifice in the
nozzle through which the material is extruded, the extruded
dielectric and/or conductive paste may in some embodiments have a
substantially square or cylindrical shape. Because the extruded and
deposited paste may undergo a settling process, or in some cases a
solidification process (for example, air-drying or thermal
treatment, such as sintering or curing) after being deposited in
the one or more layers 142, the shape of the layers 142 and the
overall shape of the impedance transformer 110, including the
respective media 118, 120 and/or conductors 114, 116, may include
some distortions. As such, the first medium 118 and the second
medium 120 may be described as having substantially planar and
parallel surfaces, substantially constant widths, substantially
wedge-shaped forms, etc., which is defined herein as having those
shapes or forms, or those distorted shapes or forms. In addition,
due at least in part to the shape of the extruded paste, settling,
or the nature of the layerwise additive manufacturing process, the
respective inclined areas 124, 128 of the dielectric media 118, 120
may depart from a perfectly sloped surface, and may instead include
some distortions or minor ridges that are about the thickness of
the deposited layer (as shown in FIG. 3, for example). As such, the
inclined areas 124, 128 as defined herein may be effectively
inclined to a plane perpendicular to the a longitudinal axis
extending along the length of the impedance transformer 110 and may
include such distortions or minor ridges.
Due to the desired functionality of the dielectric media 118, 120,
the dielectric material may be selected in a suitable manner to
provide a desired dielectric property (e.g., a desired dielectric
constant) or other characteristics. The dielectric materials may
typically exhibit good electrical insulation, for example, on the
order of about 10.sup.-4 to 10.sup.-8 siemens per meter. The
electrically conductive material for forming the conductors 114,
116 may also be selected in a suitable manner to have a desired
conductivity, or other characteristic. For example, the conductors
114, 116 may have an electrical conductivity on the order of about
10.sup.4 to 10.sup.7 siemens per meter. The respective pastes may
include a polymeric binder, such as a flowable thermoset or
thermoplastic, that includes a mixture of one or more dielectric,
magnetic, or conductive materials dispersed therein.
The dielectric paste and/or the electrically conductive paste may
be designed with an appropriate chemistry and viscosity to enable
extrusion through the nozzle and to provide the desired structures
of the media 118, 120 and/or the conductors 114, 116. Preferably,
the respective pastes have thixotropic shear thinning behavior that
enable the pastes to be extruded through the nozzle and yet be able
to retain a self-supported shape of the deposited layer 142 after
exiting the nozzle. In addition, it may be preferable that the
respective pastes have good chemical compatibility and good wetting
behavior with respect to each other, and with respect to other
circuit components, so as to form strong interfacial bonds in the
as-deposited state, as well as after any post-processing, such as
thermal treatment, without compromising the structural integrity of
the respective structures.
One advantage to additively manufacturing the impedance transformer
110 by way of layerwise deposition is that the impedance
transformer structures may be fabricated in situ, directly within
an RF module or directly integrated with the impedance matching
network, and therefore may not necessarily require subtractive
machining or etching, nor prefabrication and subsequent integration
steps. In addition, the impedance transformer 110 may be
"free-formed" in straight, circuitous, or serpentine paths, for
example, around other circuit components, or even up vertical
walls, which greatly enhances the tailorability and flexibility of
the impedance transformer and/or RF module design.
It is understood that the additive manufacturing process for
forming the impedance transformer 110 is not limited to layerwise
deposition, and may include other methods, such as, but not limited
to: Selective Laser Sintering (SLS), Stereolithography (SLA),
micro-stereolithography, Laminated Object Manufacturing (LOM),
Fused Deposition Modeling (FDM), MultiJet Modeling (MJM), aerosol
jet, direct-write, inkjet fabrication, and micro-dispense. Areas of
overlap can exist between many of these methods, which can be
chosen as needed based on the materials, tolerances, size,
quantity, accuracy, cost structure, critical dimensions, and other
parameters defined by the requirements of the object or objects to
be made.
In addition, certain additive manufacturing processes, such as
micro-dispense or fused-filament fabrication, may be adapted to
continuously vary or uniformly grade the effective dielectric
property of each individual medium 118, 120, or the combined
dielectric medium 112, along the impedance transformer 110 in the
direction of the transmission path. Such an exemplary process may
be used to create such impedance transformers as the exemplary
impedance transformer shown in FIG. 2D. For example, an additive
manufacturing extrusion printhead may be adapted to actively mix
blends of two or more dielectric materials that are fed into the
extrusion head. The composition of the blended material to be
deposited may be varied by varying the ratios of the respective
materials, which may be dependent on the feed rates of the
respective materials into the printhead, among other factors. In
this manner, the blend composition may be actively varied during
deposition to create a dielectric media with a continuously
changing or graded dielectric property. Other electrical or
dielectric properties of the individual dielectric media 118, 120
may be altered in similar manner, such as the permittivity,
permeability, and electrical conductivity. The electrical
properties of the conductors 114, 116 may also be varied in a
similar manner, for example, to adjust the electrical resistivity
of the transmission line so as to vary the characteristic impedance
of the transmission line along its length. By continuously varying
the dielectric and/or electrical properties of the dielectric media
and/or the conductors through additive manufacturing in this way
greatly improves the design flexibility and performance
characteristics of the exemplary impedance transformer.
Although the invention has been shown and described with respect to
a certain embodiment or embodiments, it is obvious that equivalent
alterations and modifications will occur to others skilled in the
art upon the reading and understanding of this specification and
the annexed drawings. In particular regard to the various functions
performed by the above described elements (components, assemblies,
devices, compositions, etc.), the terms (including a reference to a
"means") used to describe such elements are intended to correspond,
unless otherwise indicated, to any element which performs the
specified function of the described element (i.e., that is
functionally equivalent), even though not structurally equivalent
to the disclosed structure which performs the function in the
herein illustrated exemplary embodiment or embodiments of the
invention. In addition, while a particular feature of the invention
may have been described above with respect to only one or more of
several illustrated embodiments, such feature may be combined with
one or more other features of the other embodiments, as may be
desired and advantageous for any given or particular
application.
* * * * *